Sexual reproduction is the creation of new individuals resulting from the joining of the nuclei of two separate sex cells. The separate sex cells are gametes; the sperm and egg. Fertilization is the union of the two gametes, and the fertilized cell that is formed is called the zygote.

These gametes must have specific characteristics in order for sexual reproduction to work properly. Specifically, they must have only half the total number of chromosomes that normal cells of that species contain. Cells that have half the normal number of chromosomes are called monoploid or haploid cells. Thus, when the nuclei of the sperm and egg join together, instead of having twice the normal number of chromosomes, the resulting fertilized egg cell will have exactly the right number. A cell with the normal number of chromosomes is called a diploid cell. In order to form a monoploid...